CAMP LOT A NOISE TROPICALS
"Big enough to serve your Orchid needs, small enough for personal service"
YELLOW LEAVES (Dens and Vandas)
Robert M. Scully
The appearance of yellow leaves in the greenhouse is not a happy development in most cases. But where
dendrobiums are concerned, the news can be both good and bad. For example, good news probably means that
leaves on popular, pendulous cane-type dendrobiurns [D. anosmum(syn. superbum), D. pierardii,
D.parishii, D.primulinum, and D. devonianum] have already yellowed and fallen, or at least the process is well
underway. This reaction is triggered by a change in night temperatures and day-length after a period of dormancy;
and it is quite normal. If the leaves for this group of species are still in place, you probably did not assist the shift to
winter dormancy by mostly withholding water (although an occasional light sprinkling helps reduce cane shriveling)
from late October to-February. This leaf loss precedes flowering in all of the species mentioned. If your plant's
leaves are still lush and green, you mayactually be growing, them right through the spring flowering season ...
unusual but possible. Oops!! Also, Den. nobile and its hybrids can naturally lose their leaves prior to
flowering. However, since most of those which are sold in the US have originated in Hawaiii, they may be
flowering in response to natural cold treatments provided on the mountainside of Mauna Loa, home of Hawaii's
Volcano National Park, before they were "moved" to the Mainland; in many instances, these plants
do not uniformly lose their leaves before flowering. For the sake of accentuating the colorful and showy blossoms
though, you may actually strip the green leaves from the fat canes to remove obstructions to the full appreciation
of a spring flowering. Do this carefully, whether it is in one of the species first mentioned or in Den nobile.
And do it only if there are emerging buds present at the nodes. Scissors are not required; just firmly grip the
leaf to be removed at its base and roll it away from the cane along its point of connection at the node. Incidentally,
in the natural state, Den. nobile produces pendulous pseudobulbs (canes) too...just as Den.
anosmum does. But modem breeding programs deliberately selected parental types that provide excellent
basal cane strength in their offspring; so at least until burdened by a heavy flower production, the canes are
That is the good news; now for the bad! Evergreen dendrobiums, like Den. stratiotes and Den. phalaenopsis-types, should not lose their leaves in this season; but with cold nights recurring in the 52 F.
range, there will be unnatural leaf loss ... especially on the older canes. If you can protect your dendrobiums
in these categories from exposure to temperatures below 65 F, there will be less likelihood of leaf loss in the
winter. Interestingly though, this leaf loss will not keep your plant from flowering ... even on the old canes.
So, while it may be disappointing to see these leaves, there probably is minimal risk that the plant will suffer
long-term damage. And in the spring, you will get at least one beautiful lush new growth which will seem to
breathe new life into your plant.
--Vandas & Ascocendas- -
Now is the time to be on the look-out for
signs of thrip invading our orchid collection. Problem with this pest, they like the orchid flowers and buds
best. So they hide themselves in the overlapping areas of the floral parts and rasp-away on the succulent
flower tissues...finally leaving a disfiguring scar that is bound to disappoint you. Serious damage can be
inflicted in one night. And that's not all! They get into vanda buds before they have even opened, if given
the opportunity. So during this season, it is a good idea to spray your plants regularly with Orthene 75W
.... at the rate of one tablespoon/ per gallon water without a sticker spreader. You can spray
this material directly on flowers that have been slightly affected to stop the assault; and the Orthene residue
(not usually visible) will handle any late arrivals to the munching plan, almost as quickly as they land.
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